Recovery seems to be on top of every elite athlete and professional sports team’s list of priorities right now. Whether it’s sleep, nutrition, treatment, or strength training the framework has shifted away from the “no pain, no gain” mantra toward how best to ensure athletes recover so they can perform their best on competition day.

Heart rate variability (HRV) has become a popular tool for measuring how well athletes recovers from training, and thus also giving you a tool to predict of how well they may perform in future exercise bouts. What does HRV actually measure? It’s the variation in time interval between heartbeats, therefore giving you information about the autonomic nervous system (ANS).

Your ANS is broken up into two parts; your sympathetic nervous system (SNS) and parasympathetic nervous system (PNS). The SNS is the “gas pedal” that kicks up during training or when you’re busy and on the go throughout the day. It’s your “fight or flight” response. In contrast, your PNS is called the “rest and digest” nervous system because it’s activated during deep sleep and relaxation.

In general, most athletes (and people working at a desk or taking care of kids at home) are stuck in “fight or flight” SNS mode too much of the day. This burns you out and impairs future mental and physical performance.

In short, HRV gives you a measure of an athlete’s neurological fatigue. The less variance in your HRV measurement, the more you’re in “go-go-go” SNS mode (and thus increased likelihood to be rundown in the long-term). The greater the variance, the more active your PNS “recover” mode and thus the more rested your nervous system. It’s a simple measure that can be taken from a heart rate monitor or wearable device that can give you insights into your level of stress.

Recently, a study on professional baseball players was performed to examine the changes in HRV. The small study consisted of eight single-A pitchers that were measured daily over the course of an entire season. The results showed the ONLY day the pitchers had significant changes in HRV was the day after their scheduled start. While it can seem obvious that after a day of pitching a player would be fatigued, it’s interesting to be able to display and quantify and altered autonomic nervous system function.1

Over the course of the year, this has particular implications to all therapies received by the pitchers post-start. Are they travelling and not getting adequate sleep the night of a start? If so, what strategies are in place to mitigate this additional stressor? What changes to a players nutrition can be added after a game in order to blunt cortisol stress release, support inflammation response and transition player into recovery as quickly as possible?

This applies to all interventions, like the common practice of taking an ice bath after a game. Ice baths stimulate the sympathetic nervous system, therefore is this always the best approach after a game?

Of course, if you’re starting pitcher is back to 100% two days after each start, throughout the course of the season then no intervention would be needed. However, as in most sports, athlete’s baseline cortisol stress levels tend to increase as the season progresses and fatigue sets in, making the treatments all the more important as you move toward the playoffs and the most important games of the season.

The research around the use of HRV is mounting and does show promise as a good indicator of future exercise performance.2, 3 However, the data is still equivocal, meaning the results don’t always mean something and you should still take into account your physical and mental symptoms (i.e. keep a journal). You need to use your intuition as a coach or therapist – your eyes, ears and hands – to determine if the information is useful or not.

In the end, you need to choose a method of assessing fatigue in your athletes and HRV shows good promise. Whatever tool you select, you must stick with it and see what the data tells you in the long run. For baseball pitchers, new research confirms what we’ve probably known for a while… the day after a start, pitchers are tired! Only time will tell if its information worth listening to, or if it’s time to opt for another method.

Dr. Marc Bubbs

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Dr. Marc Bubbs ND, MS(c), CISSN, CSCS is a Naturopathic Doctor, Speaker, Director of Nutrition for the Canadian Men's National Basketball Team and former Strength Coach. Dr. Bubbs is the author of The Paleo Project: The 21st Century Guide to Looking Leaner, Getting Stronger, and Living Longerand a regular contributor to Re-Find Health, Breaking Muscle,PaleoDiet.com anda nutrition advisory board member forStrong Magazine. Dr. Bubbs regularly presents at health, fitness and medical conferences across Canada, USA, UK and Europe and has consulted with professional sports teams in the NBA, NFL, NHL and MLB.